1. Field of the Invention
The present invention relates to an electroluminescent panel device in which an AC drive electric field is applied to an electroluminescent layer to thereby emit light in said electroluminescent layer.
2. Prior Art
An electroluminescent panel of this kind is designed so that an electroluminescent layer comprising a flourescent material and a high dielectric material is held between electrode layers provided on opposite surfaces thereof, at least one of said electrode layers being formed as a transparent electrode, and an AC voltage is applied between these both electrodes to emit light in the electroluminescent layer.
The thus structured electroluminescent panels have been widely used as display elements for various machineries and devices, and back-light sources of displays.
In the above-described AC drive electroluminescent panel, high dielectric resins such as cyanoethyl cellulose or cyanoethylpulran, or high dielectric such as barium titanate are used as material for constituting an electroluminescent layer. Since such materials exhibit piezoelectric properties, the panel is vibrated by the AC electric field caused by application of a driving AC voltage to generate a vibration noise (buzzing).
This vibration is not only offensive to the ear but shortens the life of the electroluminescent panel and adversely influences on machineries and devices applied.